Andy travelled from 6.30 a.m. to 6.46 a.m.<br>
Time Andy travelled = 16 minutes.<br>
Distance Andy covered = 40 &times; 16 = 640 m.<br><br>
Father travelled from 6.36 a.m. to 6.46 a.m.<br>
Time father travelled = 10 minutes.<br>
Father covered the same 640 m in 10 minutes.<br>
Father's speed = 640 &divide; 10 = 64 m/min.<br><br>
Final Answer: 64 m/min